include voice services, circuit data, and packer Pos amic packet assignment(DPA) has been pro and wireless services Integrated services also d sed, with the potential to provide 384 kb/s DM can largely data with transmission rates from 30 kb/s to a data services in macrocellular environments using few hundred megabits per second. Providing only I MHz of spectrum 3]. It is possible to eliminate the nomadic customers in areas such as airports, and this acis concept into a wideband con hotels, and other public areas with the same user text in 5 MHz while providing a complementary effects of experience they have in their office is the key service to third generation systems such as driver to deploy such high-rate complementary EDGE and WCDMA. This wideband OFDM packet data services. system would support an order of magnitude interference for Wideband code-division multiple access higher peak data transmission rate in macrocells (WCDMA)will use 5 MHz channels, and it is a at 2 to 5 Mb/s and up to 10 Mb/s in microcells leading candidate for third-generation wireless IS-136, GSM or WCDMA would provide circuit transmission rates access[1]. However, it will be limited to about voice and other circuit-based services and basic 384 kb/s(nominal)peak data rates for macro- data services. A complementary high-speed cellular wireless access(up to 2 Mb/s rates are packet data mode would provide fast wireless ed for indoor environments). Global S, acket data access to meet the demand for wire tem for Mobile Communications (GSM less data in the future that provides access pe and it readily enhancements based on enhanced data rates formance similar to wideband fixed access. Since for GSM Evolution(EDGE)using adaptive portable equipment is power-limited, strongly modulation will provide bit rates up to 384 kb/s net al traffic should be supported, and interference in the near future. [1] Second-generation wire link transmission rates should be allowed to less systems will evolve with complementary adapt downward as necessary to support the suppression and packet data solutions that generally use frequen ed link budgets. Wideband oFDM wire cy channels separated from circuit voice and cir less access might also be configured to introduce cuit data access. Time-division multiple access new broadband capabilities using OFDM only coding to (TDMA)and CDMA systems are being consid- on the downlink, which is then integrated wit ered in which circuit and packet access share a emerging wireless packet data systems such as common frequency channel and access modes General Packet Radio Service(GPRS), EDgE, are separated by time slots or spreading codes. or WCDMA to provide two-way access. An However, the expected demands for high peak- example of such a system with the EDGE uplink rate Internet access are motivating increasing is discussed in[4].2 consideration of complementary access based on There are a number of reasons to consider separate frequency channels to provide maxi- such a high-rate complementary packet data mum peak rates and to allow optimization for capability for downlinks. Wireless Internet packet data transmission alone OFDM was proposed for digital cellular sys- more, for data services, peak bit rate is very tems in the mid-1980s [2]. OFDM has also beer portant in determining overall system perfor shown to be effective for digital audio and digi- mance, because of the highly bursty nature of tal video broadcasting at multimegabit rates in Internet traffic. GPRS, EDGE, and WCDMA Europe, and it has been incorporated into stan- solutions will support transmission rates of dards by the European Telecommunications 144-384 kb/s in macrocellular environments. To Standards Institute(ETSI). The IEEE 802.11 achieve rates in the megabits-per-second range tandards group recently chose OFDM modula- for all environments using -5 MHz spectrum is ion for wireless LANs operating at bit rates up challenging for both the physical layer and radio to 30 Mb/s at 5 GHz. In this article, OFDM resource management design Single-carrier modulation combined with dynamic packet TDMA solutions are limited in supportable assignment with wideband 5 MHz channels is transmission bit rate by equalizer complexity proposed for high-speed packet data wireless Even though new techniques such as interfer access in macrocellular and microcellular envi- ence suppression and space-time processing are ronments, supporting a family of peak bit rates promising, the interactions of these techniques Peak rates exceeding I sive environments, and it readily supports inter- intercode interference at high bit rates limits considered for some ference suppression and space-time coding CDMA solutions. The use of oFDM with suffi- tems enhance efficiency. Dynamic packet assignment ciently long symbol periods of 100-200 us for can support excellent spectrum efficiency and packet data transmission addresses these issues. 2 In/4 we focused on the high pea It supports a high bit rate in time delay spread architecture of such a mm in a macrocullar WIDEBAND OFDM environments with performance that improves with increasing delay spread up to a point of system. This article pro- WCDMA is now recognized as one of the lead- extreme dispersion. Another reason to consider vides a detailed discussion ng candidates for third-generation wireless a complementary packet data solution is to use of the design considera- access. Based on direct-sequence spread-spec- optimized admission procedures for packet data tions under different con- trum with a chip rate of 3. 84 Chips/s, it occu- access that is fairly aggressive in order to achieve ditions. However, the pies a bandwidth of about 5 MHz. It will support high spectral efficiency. An aggressive admission numerical results shown ircuit and packet data access at nominal rates policy will result in high word error rates in /4 were based up to 384 kb/s in macrocellular environments, (WERs) that can generally be managed for improved radio link and provide simultaneous voice and data ser- Internet services using automatic repeat reques design using convolution (ACIS) concept based on OFDM signaling and (ARQ)techniques but are problematic for al codes to achieve even vices. An advanced cellular internet delay-sensitive voice services. Therefore, a com- better performance Magazine·JuIEEE Communications Magazine • July 2000 79 and wireless services. Integrated services also include voice services, circuit data, and packet data with transmission rates from 30 kb/s to a few hundred megabits per second. Providing nomadic customers in areas such as airports, hotels, and other public areas with the same user experience they have in their office is the key driver to deploy such high-rate complementary packet data services. Wideband code-division multiple access (WCDMA) will use 5 MHz channels, and it is a leading candidate for third-generation wireless access [1]. However, it will be limited to about 384 kb/s (nominal) peak data rates1 for macro￾cellular wireless access (up to 2 Mb/s rates are proposed for indoor environments). Global Sys￾tem for Mobile Communications (GSM) enhancements based on Enhanced Data Rates for GSM Evolution (EDGE) using adaptive modulation will provide bit rates up to 384 kb/s in the near future. [1] Second-generation wire￾less systems will evolve with complementary packet data solutions that generally use frequen￾cy channels separated from circuit voice and cir￾cuit data access. Time-division multiple access (TDMA) and CDMA systems are being consid￾ered in which circuit and packet access share a common frequency channel and access modes are separated by time slots or spreading codes. However, the expected demands for high peak￾rate Internet access are motivating increasing consideration of complementary access based on separate frequency channels to provide maxi￾mum peak rates and to allow optimization for packet data transmission alone. OFDM was proposed for digital cellular sys￾tems in the mid-1980s [2]. OFDM has also been shown to be effective for digital audio and digi￾tal video broadcasting at multimegabit rates in Europe, and it has been incorporated into stan￾dards by the European Telecommunications Standards Institute (ETSI). The IEEE 802.11 standards group recently chose OFDM modula￾tion for wireless LANs operating at bit rates up to 30 Mb/s at 5 GHz. In this article, OFDM modulation combined with dynamic packet assignment with wideband 5 MHz channels is proposed for high-speed packet data wireless access in macrocellular and microcellular envi￾ronments, supporting a family of peak bit rates ranging from 2 to 10 Mb/s. OFDM can largely eliminate the effects of intersymbol interference for high-speed transmission rates in very disper￾sive environments, and it readily supports inter￾ference suppression and space-time coding to enhance efficiency. Dynamic packet assignment can support excellent spectrum efficiency and high peak-rate data access. WIDEBAND OFDM WCDMA is now recognized as one of the lead￾ing candidates for third-generation wireless access. Based on direct-sequence spread-spec￾trum with a chip rate of 3.84 Mchips/s, it occu￾pies a bandwidth of about 5 MHz. It will support circuit and packet data access at nominal rates up to 384 kb/s in macrocellular environments, and provide simultaneous voice and data ser￾vices. An advanced cellular Internet service (ACIS) concept based on OFDM signaling and dynamic packet assignment (DPA) has been pro￾posed, with the potential to provide 384 kb/s data services in macrocellular environments using only 1 MHz of spectrum [3]. It is possible to expand this ACIS concept into a wideband con￾text in 5 MHz while providing a complementary service to third generation systems such as EDGE and WCDMA. This wideband OFDM system would support an order of magnitude higher peak data transmission rate in macrocells at 2 to 5 Mb/s and up to 10 Mb/s in microcells. IS-136, GSM or WCDMA would provide circuit voice and other circuit-based services and basic data services. A complementary high-speed packet data mode would provide fast wireless packet data access to meet the demand for wire￾less data in the future that provides access per￾formance similar to wideband fixed access. Since portable equipment is power-limited, strongly asymmetrical traffic should be supported, and uplink transmission rates should be allowed to adapt downward as necessary to support the required link budgets. Wideband OFDM wire￾less access might also be configured to introduce new broadband capabilities using OFDM only on the downlink, which is then integrated with emerging wireless packet data systems such as General Packet Radio Service (GPRS), EDGE, or WCDMA to provide two-way access. An example of such a system with the EDGE uplink is discussed in [4].2 There are a number of reasons to consider such a high-rate complementary packet data capability for downlinks. Wireless Internet usage is likely to be downlink-limited. Further￾more, for data services, peak bit rate is very important in determining overall system perfor￾mance, because of the highly bursty nature of Internet traffic. GPRS, EDGE, and WCDMA solutions will support transmission rates of 144–384 kb/s in macrocellular environments. To achieve rates in the megabits-per-second range for all environments using ~5 MHz spectrum is challenging for both the physical layer and radio resource management design. Single-carrier TDMA solutions are limited in supportable transmission bit rate by equalizer complexity. Even though new techniques such as interfer￾ence suppression and space-time processing are promising, the interactions of these techniques with equalization significantly lower achievable bit rates in hostile operating environments for single-carrier solutions. Low spreading gain or intercode interference at high bit rates limits CDMA solutions. The use of OFDM with suffi￾ciently long symbol periods of 100–200 ms for packet data transmission addresses these issues. It supports a high bit rate in time delay spread environments with performance that improves with increasing delay spread up to a point of extreme dispersion. Another reason to consider a complementary packet data solution is to use optimized admission procedures for packet data access that is fairly aggressive in order to achieve high spectral efficiency. An aggressive admission policy will result in high word error rates (WERs) that can generally be managed for Internet services using automatic repeat request (ARQ) techniques but are problematic for delay-sensitive voice services. Therefore, a com￾OFDM can largely eliminate the effects of intersymbol interference for high-speed transmission rates in very dispersive environments, and it readily supports interference suppression and space-time coding to enhance efficiency. 1 Peak rates exceeding 1 Mb/s under limited condi￾tions for very few simulta￾neous users are also considered for some sys￾tems. 2 In [4] we focused on the architecture of such a system in a macrocullar system. This article pro￾vides a detailed discussion of the design considera￾tions under different con￾ditions. However, the numerical results shown in [4] were based on an improved radio link design using convolution￾al codes to achieve even better performance